Field of the Invention
The present invention relates to a light source optical system and a projection display apparatus employing the same.
Description of the Related Art
In recent years, a projector has been developed that irradiates a fluorescent body with a light flux emitted from high output laser diodes (hereinafter referred to LDs) as an excitation light, and includes a wavelength-converted fluorescent light as a light source light. In such a projector, the brightness of the projector can be increased by increasing the number of LDs and/or increasing the output of each LD.
However, the light density of a light source spot formed on a fluorescent body surface is increased when the strength of incident light onto the fluorescent body is increased to increase the brightness. As a result, a problem such as reduction of the light conversion efficiency occurs because of a luminance saturation phenomenon, and therefore, the brightness proportional to the increase in the output of the LD cannot be obtained.
A technique discussed in United States Patent Application Publication No. 2012/0133904 is known as a technique to solve such a problem. United States Patent Application Publication No. 2012/0133904 discusses a configuration in which two fly-eye lenses are provided on the latter stage of an optical system for compressing light fluxes from a plurality of LDs. Such a configuration can uniformize the light density of the light source spot formed on the fluorescent body and suppress the occurrence of an area having an extremely high light density to suppress the reduction of the light conversion efficiency described above.
The configuration discussed in United States Patent Application Publication No. 2012/0133904 requires not only the LD for exciting the fluorescent body but also an LD for guiding a blue color light to a color separating and combining system and an optical system therearound, leading to increasing the entire apparatus size.